This application claims benefit of Japanese Application No. 2001-101497 filed in Japan on Mar. 30, 2001, the contents of which are incorporated by this reference.
1. Field of the Invention
The present invention relates to the structure of frontward and rearward movable frame members which constitute a lens barrel.
2. Related Art Statement
A zoom lens barrel disclosed in Japanese Unexamined Patent Application Publication No. 11-64714 concerning the configuration of a lens barrel includes a first-group tube for supporting a first lens group, and a second-group tube for supporting a second lens group (focusing lens). The first-group tube is supported by a cam frame, and the second-group tube is supported by a zoom tube via a guide shaft. The zoom tube is supported by the cam frame.
In the above zoom lens barrel, multiple supporting members, such as the first-group tube, the cam frame, the zoom tube, and the guide shaft, are interposed between the first lens group and the second lens group, as described above. Therefore, a deviation between optical axes of the first lens group and the second lens group may increase, and this makes it difficult to achieve a high optical performance.
The present invention has been made to overcome the above problems, and an object of the invention is to provide a lens barrel with a simple configuration in which frame members are supported with high precision and in which a deviation between the optical axes of lens groups is reduced.
In order to achieve the above object, according to an aspect of the present invention, there is provided a lens barrel having a plurality of lens groups including at least a first lens group and a second lens group which are movable, along an optical axis, and also comprising a cam frame having a first cam and a second cam for driving the first, lens group and the second lens group along the optical axis during a zooming operation, a first moving frame which holds the first lens group and is driven along the optical axis by the first cam, a second moving frame which is driven along the optical axis by the second cam, a third moving frame which holds the second lens group and is supported by the first moving frame so that it can move along the optical axis relative to the first moving frame, and a driving device mounted in the second moving frame so as to drive the third moving frame relative to the first moving frame and the second moving frame along the optical axis.
According to another aspect of the present invention, there is provided a lens barrel having a plurality of lens groups including at least a first lens group, a second lens group, and a third lens group which are movable along an optical axis, and also comprising a first-lens-group moving frame which holds the first lens group, a first and a second guide members formed in the first-lens-group moving frame so as to extend along the optical axis, a second-lens-group moving frame which holds the second lens group and which is guided slidably only along the optical axis relative to the first-lens-group moving frame while the positional accuracy of the second lens group with respect to the optical axis of the first lens group is ensured to be within a predetermined range by the first guide member, and a third-lens-group moving frame which holds the third lens group and which is guided slidably only along the optical axis relative to the first-lens-group moving frame while the positional accuracy of the third lens group with respect to the optical axis of the first lens group is ensured to be within a predetermined range by the second guide member.
Further objects, features, and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.